Electrical energy generating system



Patented Jan. 4, 1944 ELECTRICAL ENERGY GENERATING SYSTEM Alfred N. Goldsmith. New York. N. Y., assignor to Radio Corporation 01 America, a corporation Delaware Application June 28, 1941, Serial No. 400,206

(Cl. 1'l8-7.5)

6 Claims.

My invention, in general, relates to alternating current generating apparatus, and more particularly to such apparatus for developing alternating current waves synchronously with other alternating current producing apparatus.

The problem of developing voltages and currents for such purposes as deflecting the cathode ray beam in the cathode ray tube contained in a television receiver would be much more simple if the same power line which energizedthe transmitting apparatus were available to a user or operator of receiving apparatus for receiving and reproducing pictures transmitted from that transmitter. This is, however, frequently not possible,,and accordingly it is an object of my invention to provide apparatus for energizing deflnite portions of a television receiver without utilizing the same power supply that energizes the transmitter. I

It is well known that for best operation of economically feasible television receivers of the electronic type it is necessary that they shall operate from a source of alternating current supply identical in frequency and phase with the alternating current supply used at the transmitting station. At the transmitter, by means of suitable electric expedients, the field frequency is rigidly tied in with the frequency of the A. C. power supply. At the receiving station there is a certain amount of leakage of A. C. magnetic or electric fields from the power unit and receiver circuits into the Kinescope deflection circuits on one hand and the Kinescope video grid control and its circuits on the other hand. Accordingly, if the A. C. supply at the receiver is not identical with that of the transmitter there will be several undesirable effects that will result. First, the line deflections will be influenced by the leakage fluxes from the local power source and its associated circuits, thus causing a variable lateral motion in the reproduced picture, this motion differing in various parts of the picture from top to bottom; and the entire variation will move up.

or down through the picture in accordance with the differences in frequency and/or phase between the local power source and the power Thirdly, the line interlacing in the received picture will be affected prejudicially by the beat phenomena referred to hereinbefore if an interlaced system is used. Line interlacing as a matter of fact, is a relatively delicate procedure according to the acecpted methods and can be accomplished effectively only under good operating conditions in the system. If interlacing is affected the image structure becomes coarse due to line pairing and image detail is also substantially reduced. The reduction of these three ef- 1'ects is possible by reducing the leakage fluxes hereinbefore referred to by extremely careful shielding of the power circuits. However, this solution is not particularly economical. The instructive discussion by Engstrom appearing in the July, 1939, edition of the Journal of the Society of Motion Picture Engineers on pages 16 and 17 thereof should be referred to in this respect. Accordingly, it is another of the objects of my invention to provide apparatus for obviating the undesirable results hereinbefore outlined which accrue from using at a television receiver a power source which difiers from the source used at the transmitter.

In order to obviate the undesirable efiects hereinbefore discussed, it is necessary that an alternating power supply be developed at the receiver which has the same frequency as, and a constant phase relationship to, the alternating current supply at the transmitting station, and accordingly it is another of the objects of my invention to provide a device by which this may be rendered feasible.

It has been brought out hereinbefore that, as one of the methods of reducing the leakage fluxes which cause undesirable efiects at the receiver under the conditions set out hereinbefore, it has been customary to use extremely careful shielding arrangements at the receiver, and it has also been brought out that the shielding arrangements are uneconomical. Accordingly, it is another of the objects of my invention to provide an arrangement for doing away with the undesired eflects hereinbefore mentioned and which will avoid the use of elaborate shielding arrangements.

In some of the older power districts in the United States there are still a number of buildings and residiences supplied only by direct current sources, or by alternating current of a relatively unusual frequency. To permit satisfactory receiver operation in such districts some local and suitable means must be provided for gencrating alternating current of the usual freat the transmitter.

quency generally used at the transmitter. It is obvious that in general such a D. C.=A. 63. conversion device will be required inasmuch as the high voltages required in a television receiver are not economically, conveniently, or safely obtainable from D. 0. equipment at the present time, Accordingly, it is another of the objects of my invention to provide an apparatus which will allow the use of a television receiver in dis= tricts where the power supply is direct current.

Accordingly, among the objects of my inven tion are:

1. To provide apparatus for energlzlngdeilnite portions of a television receiver without utilizing a connection to the same power supply that energizes the transmitter.

2. To provide apparatus for obviating unde= til sirable results hereinbeiore outlined which accrue from using at a television receiver a power source which differs from the source used 3 To provide a device by which a developed alternating current at the receiver is maintained constant in frequency and phase relationship to the alternating current supply at the transmitter.

4. To provide an arrangement for doing away with undesired efiects hereinbeiore mentioned, and which will avoid the use of elaborate shielding arrangements.

5. To provide an apparatus which will allow the use of a television receiver in districts where the power supply is direct current or alternating current oia difierent frequency from that oi the are normally picked up by the television receiver.

The filtered output of the labile oscillator then is used to control the generation of an alternating current by means such as a thyratron oscillator, for instance, and the latter oscillator itself is energized from the non-synchronous power supply. The output of the latter oscillator then may be used to energize portions or all of the television receiver. Since the controlling or labile oscillator is controlled by the field synchronizing signals, whichin turn bear a. definite relationship to the frequency of the power supply at the transmitter; the generated waves thus will be in phase with, and of the same frequency as, the source ofpower at the transmitter.

My invention will best be understood by reference to the single figure of the drawing which schematically shows one embodiment thereof.

Referring to the drawing, which shows a sche-- matic embodiment of my invention, the power supply ID at the receiver is shown, and it is assumed that this power supply varies in frequency and phase from that of the transmitting station. There is provided a labile oscillator I I; and this oscillator may be of any type which will oscillate freely at some frequency to which it may be set, and which will also shift: easily and immediately to the frequency of an impulsive or alternating source impressed upon a. control member thereof; and the non-synchronous assures power supply may be used to energize (but not to control the frequency of) the labile oscillator. For example, such a labile or frequency control oscillator might be the well-known blocking oscillator, or a multi-vibrator, or the like. if such an oscillator were set to a frequency somewhat below 30 cycles and permitted to oscillate at that frequency, incoming field frequency oscillations of 69 cycles, or a value close thereto, impressed upon its grid or control member with suitable amplitude would trigger this oscillator and therefore force it to follow accurately the fre quency and phase of the field impulses, the latter being, as stated, of 6d cycle frequency, by way of example. Therefore, the most effective and convenient setting of the free frequency of the labile oscillator is slightly lower than the con trolling frequency impressed thereon. The labile oscillator, as illustrated in the drawing, comprises a well-known type of such oscillater and is described, for instance, in. the book Television by Zworylrin and Morton, first edi tion, page 256 thereof. This oscillator comprises, in general, a three element thermionic tube iii, having a condenser l3 shunted across the anodecathode space discharge path thereof and having the space discharge path or a diode M with its appurtenantpower supply indicated at PS also shunted across the condenser in order to charge the condenser. Discharge of the stored charge takes place across the anode-cathode space discharge path of the triode l2. Since conduction in the tube l2 may be initiated by impulses applied to the control electrode thereof, it will be seen that the frequency of the oscillater may be controlled by signals originating externally thereto (and applied via path 40). The filter it is of band-pass variety, and passes predominantly a sinusoidal component of fundamental frequency (in this illustrative case, cycles). The output of the labile oscillator may be impressed through the filter l5 onto the control grid of a thermionic tube IS, the latter forming a part of a frequency-controlled generator. If the power produced is suflicient, the element may be an alternating current amplifier. If the device, as used, comprises a thyratron generator, it may be controlled as to frequency and phase by the signal passing through the filter member 15 and impressed on the control gridj of the thermionic tube Hi. This particular device, as illustrated in the figure, is described on page 818 of the periodical Electrical Engineering for December, 1933, in an article on The D. C. power supply indicated as PS, these elements also being shunted across the anode-cathode space discharge path of the tube IS. The

inductive member I! comprises the primary of a transformer whose secondary 2| output passes indicated as enclosed by the dashed lines 30. Such an arrangement is used in some television practice and is illustrated, for instance, in the aforementioned book of Zworykin and Morton on page 526 thereon. The separating circuit for the synchronizing signals is indicated on pages 465 and 551 of the aforementioned book. schematically shown, the television receiver may comprise an RF tuner followed by'a first detector into which are fed the signals from a heterodyne oscillator,

the output of the first detector being fed through a first intermediate frequency amplifier, thence to a second detector, and thence to a further amplifier. A portion of the output of the'latter oscillator is fed to a synchronizing signal separator shown schematically as a thermionic tube 3| having a time constant circuit comprising condenser 32 and resistor 33 connected in the control electrode-cathode path thereof, and having a resistor 34 connected serially with a power supply indicated as SPS, this serial connection being shunted across the anode-cathode space discharge path thereof, and having the serial connection of a condenser 35, resistor 33, and condenser 31 also shunted across the anode-cathode space discharge path. Accordingly, there may be taken off by way of conductor 40 a portion of the horizontal synchronizing signals and this may be amplified,

' if so desired. The remainder of the signals pass to the normal deflection circuits of the cathode ray tube indicated schematically at 4 I The synchronizing signals may be divided out by the apparatus to the right of the line HS, and identified by thenumerals 35, 36,31, such an arrangement being the same as that described by Zworykin and Morton in Television on page 553 thereof.

As indicated in the drawing in' the legend under the element II, when the system isoperated freely without external control it will oscillate at less than the fieldfrequency, and the power output from the frequency-controlled generator 50 passes by way of conducting means to the receiver plate supply power unit of television receiver 30; and this frequency will be of some frequency slightly lower than a field frequency of a received signal. However, as soon as the television receiver becomes operative the field synchronizing signals appear in the synchronizing signal separator thereof. A portion of the syn- 'chronizing signals pass by way of a conductor to the remainder of the receiver where they are utilized in a conventional fashion. Another portion passes by way of a conducting means 40 into the labile oscillator ll, being applied to the frequency-controlling circuit thereof in such fashion as to force the oscillator H to follow accurately in frequency and phase the incoming field synchronizing signals, and this forms an essential element in the invention. If necessary,.an

amplfiier (not shown) may be interposed in conducting means All between the receiver and the labile oscillator. Thus, as indicated in legend form under the elements II and IS, the second operation, as soon as the television receiver is energized and operative, will be such that an accurately synchronized power supply will pass by conducting means 22 into the television receiver 30, and more specifically into its power supply unit, thus giving an operation which is free from the defects which have been listed hereinbefore.

A fixed shadow, corresponding to synchronized A. C.supply of constant phase relationship, might nevertheless exist in the field of the picture; and although this in in general unobjectionable in a properly designed receiver, it maybe preferable, in particular receivers and for individual Kinescopes and their associated deflecting circu ts, with whatever degree of linearity such deflecting circuits might possess, to be able to place the tween the labile oscillator and the element 53.

On the other hand,'the phase delay or shifting device may be introduced into a suitable portion of the circuits of the elements II or 50. Such a variable phase shifter then will move the fixed field shadow to any desired horizontal band in the field and will enable, in any specific instance, such band to be minimized as to its pictorial effect.

The following sequence of operations should be utilized for the most successful or effective use of the arrangements illustrated in the drawing. First, the non-synchronous power supply l0 should be connected first to the labile oscillator which thus is set into operation. Secondly, the non-synchronous power supply then should be connected to the A. C. amplifier or generator 50. The generator 50 may be of the thyratron type which operates safely with suitable alternating current excitation. ,A relay may be provided whereby power can pass through the conducting means adjoining the non-synchronous power supply to the element 50 only if the labile oscillator II has. its usual full alternating current or impulsive output. Alternatively, a time delay arrangement may be inserted in the conductor which joins the non-synchronous power supply to the element 50, which will close the circuit from the element Hi to the element 50 only after vision receiver. Thereupon synchronizing signalspass from the synchronizing signal separator element to the element ll, giving the desired receiver operation free from defects.

There are possible variations from the arrangements which have been set out hereinbefore which fall clearly within the scope of this invention as, for example, in the first variation, if we assume that certain portions of the receiver circuits are found to be relatively harmless in producing the undesired effects due to stray fields and the like which have been discussedhereinbefore, such portions of the receiver may be fed independently through a conductorwhich may join such non-critical portions of the receiver to the non-synchronous power supply. As a result, the amount of power drawn from the A. C. generator 50 will be reduced, and thus the auxiliary equipment necessary for receiver operation in nonsynchronous districts will be reduced. It will be appreciated, therefore, that although some nonsynchronous power may be utilized in the opera tion of a television device, the spirit of my invention is the provision of an arrangement by which synchronous power may be developed from a nonsynchronous supply, and accordingly, even though small parts of synchronous power might conceivably be used in some arrangements, it will be appreciated that this will fall fairly within the spirit of my invention and the scope as defined in the hereinafter appended claims.

The second variation may consist in an arrangement which takes advantage-of the fact that labile oscillators of the type which are used in the element it exist in the television receiver itself in many instances. If such oscillators can be energized independently from the non-syn chronous source 4 ii without giving rise to the up. desired defects which have been dlscussedhereinbeiore, the labile oscillator it may be omitted,

and the conducting means from the synchronizing signal separator to the labile oscillator and the one from the oscillator to the element 5i! may be joined to form a continuous single conductor. As a sub-variation, the labile oscillator in. the ten evisicn receiver may be only temporarily connected t the non-synchronous power supply, being thereafter thrown over to energlzation. through the conductor bearing the synchronous power as soon as the receiver is in full operation by means oi an arrangement such as a high speed switch and/or an associated inductance and/or capacity energy storing circuit to bridge over the change over instant.

The third variation may consist in that in general no special protective means beyond those hereinafter referred to in this specification will be required for the element 50, even though it be of the thyratron type. As long as power is supplied to elements H and 58 from the non-synchronous source, the element 50 should operate normally. Protective means may, however, be

supplied whereby if labile oscillator ll ceases to produce an output which will pass along the conductor from the labile oscillator to the element 50, the A. C. generator 50 is disconnected immediately from the power supply.

In view of the fact that in this specification there has been. referred to the use of a synchronizing signal as the signal which is indicative of the frequency and phase of the power for the transmitter, it will be appreciated, therefore, that the synchronizing signal must be either derived from the power source at the transmitter or must be derived in such a fashion that it will truly represent the frequency and phase of the power supply for the transmitter. It will be aD= preciated that the synchronizing signal itself need not be of the same frequency as that of the power supply for thetransmitter', since it may be a multiple thereof, and there may be derived from well known apparatus a signal which is a multiple or a sub-multiple of the synchronizin frequency, and which will be the correct frequency for the power supply for the transmitter.

By way of example, it may be that the frame synchronizing frequency may beof the order of 60 per second, such as is common in some present interlaced systems, and if this be the case then, at the transmitter, the synchronizing signal is deeases rived directly from the power supply for the transmitter, which supply is usually cycles.

On the other hand, in some color television systems it may be necessary to send a frame synchronizing signal which is higher in frequency than the 60 cycle power supply. If this be the case, and such is commonly the case, then, as-

suming by way of example, that the frame syn- I chronizing frequency is 180 pulses per second, then upon receipt of these pulses and separation of the pulses from the horizontal or line .synchronizing signals, the frequency of these pulses may be reduced by well known apparatus so that a sub-multiple frequency of 60 cycles is obtained.

Since the sub-multiple frequency bears a definite 7 relationship to the frequency and phase of the wave from which is derived the sub-multiple, it

will be appreciated that the derived sub-multiple wave will truly represent both the frequency and the phase oi the power supply for the transmitter. in such a case, the sub-multiple deriving apparatus might be inserted, for instance, between the labile oscillator and thesynchrcnizing signal separating means. Conversely, if the received frame frequency were lower it would be possible to multiply the frequency by well known apparatus so as to provide a 60 cycle wave, it being assumed that 50 cycles is the frequency of ,the power supply for the transmitter.

There is provided, in addition, in a schematic showing, a filament supply apparatustii and a plate supply apparatus Si. The latter must furnish smooth and filtered direct current. The outputs of the filament supply unit and the plate supply unit are respectively indicated by PS and PS. They may be connected to those points in the elements ii, 50, and 30, as indicated. The frequency controlled generator 50 produces an alternating current output which passes by way oi conductor 22 to a receiver plate supply power unit 552 in the assembly of the receiver indicated as 3d. which produces a synchronized plate supply output, so to speak, which is identified as SPS.

.supply substantially synchronous with a remote power supply by means of a control system wherein is included a local labile oscillator, a local generator and a rectifier which comprises the steps of receiving signal energy'from a selected point of transmission with the signal energy being at least in part indicative of the frequency of the power supply source at the transmitting point from which the signals were initiated, controlling the frequency at 'which oscillations are generated by the local labile oscillator under the influence of the received indicial signal energy, utilizing the controlled frequency labile oscillator output to control the oscillation frequency of the local generator to cause it to generate oscillations of a frequency substantially identical to the remote power supply at the transmitting point, supplying power to the local labile oscillator and local generator from a local non-synchronous power supply source, rectifying the controlled frequency energy output from the local power supply generator, and energizing at least a portion of the receiver from the rectified local synchronized generator output.

2." The method of supplying power to a television receiver wherein is included a local labile oscillator, a local generator for generating power at a frequency substantially identical to that of a remote power supply which controls the frequency at which the image fields are repeated in transmission, and a rectifier for rectifying the local generator output, which comprises the steps of receiving from a point, of transmission signal energy of which at least a portion there-.- of is indicative of the frequency of the power supply at the transmitting point, generating oscillations by the local labile oscillator and controlling the frequency thereof by the received indicial signal energy, utilizing the controlled complete receiver from the rectified local syn 4 chronized generator output. 3. The system for generating local power supply energy which is substantially synchronous with that of a remote po er supply which comprises a signal receiving means for receiving signal energy of which at least a portion is indicative of the frequency of the remote power supply, a local labile oscillator, means to control the frequency of oscillation of the local labile oscillator by the said received indicial signal energy, a local power supply generator, means to control the frequency of the local power sup ply generator by the labile oscillator output so that the local power supply generator frequency is substantially identical to that of the labile oscillator and that of the remote power supply, means to energize each of the local labile oscillator and local generator from a non-synchronous power supply while controlling their frequency of oscillation from the incoming indicial signals and the labile oscillator output respectively, and means to rectify the local power tively, and means for rectifying the output of the local power supply generator for energizing I at least a portion of the television receiver from the output of the synchronized local generator.

5. A device for supplying substantially .sinu- I soidal alternating current power to energize a television receiver through its rectifier which reder the influence of the indicial signals to bring ceiver is adapted to receive video and indicial signals from a field frequency control point of remote transmission, including means to transfer indicial signal energy from the television-receiver to the device with the said indicial signal energy being indicative of the frequency of a remote power supply source energizing the transmitter whereat the indicial signals originate, a local labile oscillator, means for controlling the oscillation frequency of the labile oscillator unthe said frequency to equality with the power supply frequency at the point of'indicial signal origin, a local power supply generator for developing substantially sinusoidal alternating current energy; means controlled by the labile oscillator to establish frequency identity between all of the local generator, the labile oscillator and the remote power supply source, and means for establishing a connection of the local generator output energy to the television receiver supply generator output to supply operating voltages to said receiver apparatus.

4. A power supply system for interlocking television receiver operation with a remote power supply serving to establish the frequency at' which television image field scannings are repeated in transmission which comprises receiver apparatus, for receiving signal energyv from the transmitting point of which at least a portion of said signal energy is indicative. of the frequency of the remote power supply, alocal labile synchronous power supply while controlling their,

oscillation frequency from the incoming indicial signals and the labile oscillator output respecrectifier apparatus to power the television receiver by energy stabilized by and interlocked infrequency with the power supplyat the point of indicial signal origination.

6. A power supply system for interlocking television receiver operation with a remote power supply serving to establish the frequency at which television image field scannings are repeated in transmission which comprises receiver apparatus for receiving television and indicial signal energy from the transmitting point of which at least a portion of said signal energy is indicative of the frequency of the remote power supply, a local labile oscillator, means to bring the frequency of the local labile oscillator to equality with that of the remote power supply by controlling the labile oscillator under the influence of the received frequency indicial signals, a local power supply generator for developing substantially sinusoidal alternating current energy, means to control the oscillation frequency of the local power supply generator from the labile oscillator output so that the local power supply generator frequency is substantially identical to that of the remote power supply at the transmitting'point, and means supplying the developed synchronized alternating current energy to rectifier apparatus of the television receiver, whereby electro-optical image reproduction in the television receiver is stabilized and interlocked with the transmitter whereat the indicial signals originate.

ALFRED GOLDSMITH. 

